The present invention is related to a device in which a variable high voltage can be generated. The present invention is equally related to the use of such a device and to a method of generating a high voltage.
The present invention is equally related to the use of a high voltage generating device according to the invention, wherein the output voltage magnitude is determined by inputting said digital input. The present invention aims to provide a high voltage generating device which does not suffer from the disadvantages of existing devices.
In a first aspect of the invention, high voltage generating device, wherein a variable high voltage output voltage can easily be selected, is presented. Said high voltage generating device exploits current control of the high voltage generating component (e.g., charge pump), within said device in combination with feedback control from said output voltage to said current control circuitry.
A high voltage generating device is thus presented with a charge pump/high voltage generating component having as input a voltage signal constructed by a current control circuit inputting at least one feedback current related to the output voltage generated by said charge pump/high voltage generating device. Alternatively, said high voltage generating device can be described as comprising a charge pump/high voltage generating component having as input a voltage signal constructed at least by comparing a reference current and a feedback current being related to the output voltage generated by said charge pump/high voltage generating component.
In a first embodiment of said first aspect, said device further comprises a voltage to current converter, generating said feedback current from said output voltage.
In a second embodiment of said first aspect, said device comprises a current comparator generating said voltage signal by comparing said reference current and said feedback current.
In a third embodiment of said first aspect, one recognizes that the choice of current control of said high voltage generating component enables a flexible operation of said device, meaning easy selection of the required output voltage. A high voltage generating device with variable output voltage (within certain range, of course) is obtained.
In a further embodiment thereof, the variability of said output voltage is obtained by introducing an easy modifiability of said reference current by constructing it as a combination of a plurality of basis currents, preferably a linear combination, thus summing of basis currents being multiplied with a certain constant. Said basis currents are selected to be currents with a substantially different value. Said multiplication constant is preferably one or zero, which enables the use of a digital input. The high voltage generating device comprises circuitry wherein each of said plurality of substantially different valued basis currents is selected to be part of said combination based on a digital input to said circuitry. Within said device multiplying circuitry and a current combination part is found. Said multiplying can be adapted such that it takes into account the digital nature of the signals, thus the fact that either selection (in case of a 1) or no selection (in case of a 1) of the basis current under consideration must be realized.
In a further embodiment of the invention, preventions against oscillations are taken by introduction of hysteresis, more in particular by adapting the reference current according to said input voltage. This is realized by making the reference current slightly adaptable, meaning with a certain range, based on the input voltage of said high voltage generating component. Said range for adapting is smaller than the level of the basis current with the smallest level. In this way, the charge pump remains in the activated or disabled state for a longer period of time thereby preventing all kinds of instabilities.
In a second aspect of the invention, a flexible method for generating high voltage outputs is presented. Said method is flexible because a variable high output voltage is selected by inputting a digital input signal, further used for constructing a reference current as a (linear) combination of basis currents with substantially different current values wherein each of said basis current being selected to be part of said (linear) combination according to said digital input signal. Said method is further characterized in that a feedback loop is present, meaning that the generating of the output voltage is related to an input voltage constructed by comparing said reference current with a feedback current being related said output voltage.
In a third aspect of the invention, the use of a high voltage apparatus, more in particular the selection of said variable output voltage based on a digital input is presented.
The present invention is related to a high voltage generating device comprising a high voltage generating component, generating an output voltage and having as input a voltage signal constructed at least by comparing a reference current and a feedback current, a voltage to current converter, generating said feedback current on the basis of said output voltage, and a means for adapting said reference current according to said voltage signal.
According to an exemplary embodiment, the device of the invention is supplied by a low supply voltage, and said output voltage is equal to or higher than said supply voltage.
The device of the invention may further comprise a current comparator, generating said voltage signal by comparing said reference current and said feedback current.
According to an exemplary embodiment of the device of the invention, said high voltage generating component is a charge pump, in particular comprising an inductance, a capacitance, and an external oscillator.
In the device according the invention, said reference current is constructed as a combination of a plurality of basis currents, wherein said combination may be a linear combination.
The device according to the invention may comprise circuitry wherein each of said plurality of basis currents is selected to be part or not to be part of said combination based on a digital input to said circuitry. Said circuitry comprises a voltage to current converter to provide basis currents based on a voltage reference, a means for multiplying said basis currents with a coefficient, said coefficient being the logical value of one of a first set of input control bits, a means for summing said basis currents after said multiplying, said summing resulting in said reference current.
In the device of the invention, said reference current is adaptable according to said voltage signal within a range being smaller than the current level of the basis current with the smallest level. According to an exemplary embodiment of the invention, this is obtained by a hysteresis block, said block comprising a voltage to current converter for providing a plurality of basis currents, a means for multiplying said basis currents with a coefficient, said coefficient being the logical value of one of a second set of input control bits, a means for summing up said basis currents after said multiplying, a means for multiplying said summed current with a coefficient, said coefficient being the digital output of said current comparator, and a means for adding said current after said multiplying to said reference current.
According to an exemplary embodiment, said device is designed and fabricated in a 100V c07 I2T technology.
The present invention is equally related to a method for generating a high voltage comprising the steps of inputting a digital input signal, constructing a reference current as a combination of basis currents with substantially different current values wherein each of said basis currents is selected to be part or not to be part of said combination on the basis of said digital input signal, and generating an output voltage being related to an input voltage constructed by comparing said reference current with a feedback current being related to said output voltage.